Learning Resources

URLs

In computing, a uniform resource locator (URL) is a specific character string that constitutes a reference to an Internet resource.

A URL is technically a type of uniform resource identifier (URI) but in many technical documents and verbal discussions URL is often used as a synonym for URI.

Every URL consists of some of the following: the scheme name (commonly called protocol), followed by a colon, two slashes,[note 1] then, depending on scheme, a server name (exp. ftp., www., smtp., etc.) followed by a dot (.) then a domain name[note 2] (alternatively, IP address), a port number, the path of the resource to be fetched or the program to be run, then, for programs such as Common Gateway Interface (CGI) scripts, a query string,[7][8] and an optional fragment identifier.[9]

The syntax is:
scheme://domain:port/path?query_string#fragment_id

The scheme name defines the namespace, purpose, and the syntax of the remaining part of the URL. Software will try to process a URL according to its scheme and context. For example, a web browser will usually dereference the URL https://example.org:80 by performing an HTTP request to the host at example.org, using port number 80. The URL mailto:bob@example.com may start an e-mail composer with the address bob@example.com in the To field.

Other examples of scheme names include https:, gopher:, wais:, ftp:. URLs with https as a scheme (such as https://example.com/) require that requests and responses will be made over a secure connection to the website. Some schemes that require authentication allow a username, and perhaps a password too, to be embedded in the URL, for example ftp://asmith@ftp.example.org. Passwords embedded in this way are not conducive to secure working, but the full possible syntax is

scheme://username:password@domain:port/path?query_string#fragment_id

The domain name or IP address gives the destination location for the URL. The domain google.com, or its IP address 72.14.207.99, is the address of Google's website.

The port number is optional; if omitted, the default for the scheme is used. For example, https://vnc.example.com:5800 connects to port 5800 of vnc.example.com, which may be appropriate for a VNC remote control session. If the port number is omitted for an https: URL, the browser will connect on port 80, the default HTTP port. The default port for an https: request is 443.

The query string contains data to be passed to software running on the server. It may contain name/value pairs separated by ampersands, for example ?first_name=John&last_name=Doe.

The fragment identifier, if present, specifies a part or a position within the overall resource or document. When used with HTTP, it usually specifies a section or location within the page, and the browser may scroll to display that part of the page.

Website addresses, or URLs, must meet the following standards:

They are as logical and clear as possible and make sense to people not familiar. E.g., registrar, not registr.

They are as short as possible, not exceeding 16 numbers and/or letters. E.g., dining, not diningservices.

They do not repeat unless it is necessary for marketing goals. E.g., wesley, not smuwesley.

They only contain letters, numbers, and the underscore and dash characters.